Laminated light guide collimator

ABSTRACT

The subject matter disclosed herein relates to an optical device comprising: a light guide film to transport light rays via total internal reflection; a first optical layer covering at least a portion of a first side of the light guide film, the first optical layer to receive an exiting portion of the light rays; a second optical layer covering at least a portion of the first optical layer; and a grating pattern located at an interface between the first optical layer and the second optical layer to out-couple light rays travelling in the light guide film, wherein the grating pattern is configured so that the exiting portion of the light rays transmit through the grating pattern twice before being total internally reflected by the grating pattern.

BACKGROUND

Modern electronic devices typically have user interfaces that includehigh-quality displays (e.g., color, greater than 300 ppi, and 800:1contrast ratio). These electronic displays are found in numerous typesof electronic devices such as include electronic book (“eBook”) readers,cellular telephones, smart phones, portable media players, tabletcomputers, wearable computers, laptop computers, netbooks, desktopcomputers, televisions, appliances, home electronics, automotiveelectronics, augmented reality devices, and so forth. Electronicdisplays may present various types of information, such as userinterfaces, device operational status, digital content items, and thelike, depending on the kind and purpose of the associated device. Theappearance and quality of a display can affect the user's experiencewith the electronic device and the content presented thereon.Accordingly, finding ways to enhance user experience and satisfactioncontinues to be a priority.

Increased multimedia use imposes high demands on designs of displaymodules, as content available for mobile use becomes visually richer. Ina liquid-crystal display (LCD), energy efficiency, among other things,can be determined by a backlight or frontlight design. Many conventionaltransmissive electronic displays use backlights that light up a displayto enable a viewer to see content on the display that can otherwise bedifficult to see without the backlights. In another example,conventional reflective displays use frontlights to improve visibilityof content on displays, particularly in low light situations.

Electronic devices configured with backlights and/or frontlights canincorporate one or more light guides to direct light from a light sourceonto or through a display. In some applications, a light source can havea relatively small area, such as in the case of a light emitting diode(LED).

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to non-limiting andnon-exhaustive embodiments shown in the accompanying figures. The samereference numerals in different figures refer to similar or identicalitems.

FIG. 1 is a cross-section of a light guide with a blazed grating,according to some embodiments.

FIG. 2 is a close-up view of a blazed grating, according to someembodiments.

FIG. 3 is a cross-section of a light guide, according to variousembodiments.

FIG. 4 is a close-up view of a grating pattern of a light guide,according to several embodiments.

FIG. 5 is a cross-section of a light guide with a beam steeringstructure, according to various embodiments.

FIG. 6 is a close-up view of grating patterns of a beam steeringstructure, according to some embodiments.

FIGS. 7A-7E show a process of fabricating a light guide and beamsteering structure, according to various embodiments.

FIG. 8A is a plot of distribution of light exiting a laminatedcollimator, according to some embodiments.

FIG. 8B is a close-up view of grating patterns of a portion of a beamsteering structure, according to various embodiments.

FIG. 9 is a laminated collimator including a beam steering stack,according to some embodiments.

FIG. 10 illustrates an example electronic device equipped with a lightguide, according to some embodiments.

DETAILED DESCRIPTION

Overview

This disclosure describes, in part, electronic devices that includedisplays for presenting content and other information. In some examples,the electronic device may also include one or more additional componentsassociated with the display, such as a touch sensor component layeredatop the display for detecting touch inputs, a front light or back lightcomponent for lighting the display, and/or a cover layer component,which may include antiglare properties, antireflective properties,anti-fingerprint properties, anti-cracking properties, and the like.This disclosure also includes techniques for assembling electronicdevices including these component stacks for the displays and otherfeatures described herein.

In some examples, the display may include an outer layer or protectivesheet applied during manufacture of the display. The protective sheet isa transparent sheet that overlies and protects an image-displayingcomponent of the display such that the image-displaying component isviewable through the protective sheet. When assembling an electronicdevice, one or more additional components may be stacked on top of orotherwise coupled to the protective sheet to produce a display assemblyof the electronic device. In some cases, the one or more additionalcomponents are coupled to the protective sheet by a liquid opticallyclear adhesive (LOCA) that adheres the additional component(s) to theprotective sheet. The LOCA may be cured through photo initiation usingultraviolet (UV) light.

In various embodiments, an optical device, such as a laminatedcollimator, can distribute light from a small-area light source to arelatively large area of a display or other device as described herein.For example, a laminated collimator can distribute light from one ormore light emitting diodes (LEDs) to regions of a display where thelight can be used for illumination, such as backlighting orfrontlighting for LCD-based displays.

In a number of implementations, a laminated collimator can distributelight uniformly across an area behind or in front of a pixelated displayplane. In various implementations, a laminated collimator can allow formodulating or adjusting light output intensity over time for particularlocations of an area behind or in front of a pixelated display plane.For example, changing the orientation (e.g., tilting) of a non-symmetricgrating pattern (e.g., a blazed grating or a binary-type grating), canchange the angle in which the pattern is oriented toward a light source.Accordingly, light intensity at a pixel can be modulated by turning thepixel. In another example, the density of a grating pattern can bechanged to modulate or adjust light output intensity. Grating densityrefers to a ratio of area of grating pattern to an area of non-patternedsurface. For example, pattern density of a grating can be low near alight source while pattern density of the grating can increase withincreasing distance from the light source.

In at least one embodiment, a laminated collimator can include a lightguide and one or more beam steering structures. For example, a lightguide includes a light guide film and a composite optical coatinglaminated to the light guide film. The composite optical coatingincludes a first optical layer, a second optical layer, and a gratingpattern. The first and second optical layers can be applied or depositedonto the light guide film by techniques other than lamination, andclaimed subject matter is not limited in this respect. The first opticallayer can cover at least a portion of a side of the light guide film. Aside of the first optical layer opposite to the side of the firstoptical layer that forms an interface between the light guide film andthe first optical layer can include the grating pattern. The secondoptical layer can cover at least a portion of the first optical layerand its grating pattern. In some implementations, a non-gaslow-refractive index (LRI) boundary layer can at least partially coverthe second optical layer. Accordingly, for proper operation, a laminatedcollimator as described herein need not be surrounded by air or othergas having an index of refraction near 1.0. Instead, a laminatedcollimator is operable in any medium, providing an advantage in thatindices of refraction of materials contacting exterior portions of alaminated collimator need not be considered. In other words, materialscontacting exterior portions of a laminated collimator need not affectits performance. A laminated collimator having this feature, amongothers, can be useful for some types of displays, such as displaysincorporating some color e-inks and front-light LCD technologies, justto name a few examples.

A grating pattern in a first optical layer of a light guide can beconfigured to out-couple light rays travelling in a light guide film ofthe light guide. Out-coupling occurs while the light rays travel in thelight guide film. Light rays travel in the light guide film with adistribution of angles. For example, some of the light rays can beoutcoupled because of the presence of a composite optical coating. Inorder for light rays to be outcoupled or transmitted to outside of thefilm when they strikes the inside surface of the film, the outcoupledlight rays have to be traveling in the light guide film within aparticular range of angles; otherwise the light rays will internallyreflect back into the light guide film. Herein, the term “out-couple”refers to the portion of light rays being directed out of the bounds ofthe light guide film from the light rays traveling in the light guidefilm. When light rays strike the grating pattern, the light rays can bediverted to outside the light guide film. Such diverted light rays canexit the light guide film at an angle that is undesirable for someapplications. For example, frontlighting or backlighting displayapplications can operate with light that exits from a surface at or lessthan a relatively small angle (e.g., at least about 5 to at most about10 degrees) from the normal to the surface. Thus, a laminated collimatorcan further include a beam steering structure covering at least aportion of the light guide film. Such a beam steering structure can bendlight rays by any angle. Accordingly, excessively large angles of lightrays exiting a light guide can be “corrected” to smaller angles when thelight rays traverse a beam steering structure. Mathematically, a surfacenormal is a unit vector perpendicular (e.g., 90 degrees) to a surface.As used herein, a surface normal is used to provide a referencedirection when discussing directions that light rays travel throughoptical materials or structures.

In some embodiments, a laminated collimator can provide a number ofbenefits. For example, a laminated collimator can allow for a higherdegree of collimation compared to that of various blazed gratingtechniques (described below). Another benefit is that a laminatedcollimator can generate less than about half the amount of undesirablestray light that can be generated by various blazed gratings. Yetanother benefit is that a laminated collimator can generate relativelylow levels (e.g., less than about 5.0%) of back-scattered light comparedto various blazed gratings. This feature can be particularly useful inapplications that involve opposing light propagating directions withrelatively low cross-talk. For example, patterns in a laminatedcollimator can affect light travelling from left to right along thelaminated collimator, while the patterns need not affect lighttravelling from right to left. In particular, light rays travelling fromright to left substantially preserve their propagation angles and staywithin the laminated collimator while light rays travelling from left toright may be out-coupled out of the laminated collimator. Accordingly, asingle laminated collimator can be used for multiple purposes at thesame time. For example, the laminated collimator can simultaneouslytransfer IR signals from ambient sensors or use two light sources onopposite ends of a light guide and create isolated areas that aresensitive to only one of the two light sources. This makes it possibleto change the appearance of an illuminated area by changing which lightsource is active. This could be used, for example, to createform-changing illuminated icons. These and other benefits can beimportant for any of a number of applications, such as backlighting orfrontlighting for relatively large LCD-based displays, or displays thatincorporate relatively thin optical foils or layers.

In some embodiments, a beam steering structure can include a number oflayers. For example, a beam steering structure can include a surfacefilm, a first patterned layer, and a second patterned layer. The secondpatterned layer can include a first beam-steering grating pattern at aninterface between the first and the second patterned layers. The firstbeam-steering grating pattern and the second beam-steering gratingpattern can be configured to steer light rays crossing the light guidetoward a normal of the surface film. A plurality of beam steeringstructures (e.g., a beam steering stack) can be layered to cumulativelyaffect an angle of a traversing light ray. In particular, the firstbeam-steering grating pattern is configured so that light rays thatcross the light guide film transmit through the first beam-steeringgrating pattern once before being total internally reflected by thefirst beam-steering grating pattern. The second beam-steering gratingpattern is configured so that light rays reflected from the firstbeam-steering grating pattern transmit through the second beam-steeringgrating pattern exactly once so as to change a direction of travel ofthe transmitted light rays.

In some embodiments, an optical device that includes structuresdescribed herein can be incorporated in a display. Such a display cancomprise a portion of a system that includes one or more processors andone or more computer memories. A display module can be stored on the oneor more memories and can be operable on the one or more processors tomodulate light rays that are out-coupled from a light guide of theoptical device.

In some embodiments, a light guide film, first and second opticallayers, an LRI boundary layer, and components of a beam steeringstructure can include any of a number of types of glass or plasticmaterials, which can be selected based, at least in part, on theirrespective indices of refraction.

Light discussed in embodiments need not be limited to the visibleportion of the spectrum. Instead, light can include electromagneticradiation in any portion of the spectrum, including ultra-violet,visible, and infrared.

Illustrative Environment

FIG. 1 is a cross-section of a light guide 100 incorporating a blazedgrating 102 and a light guide film 104, according to some embodiments. Afew example light rays 106 and 108 are shown. Light can travel within alight guide film 104 via total internal reflection (TIR). For example,light ray 106 internally reflects at a point 110 of an interface betweenlight guide film 104 and a surrounding medium 112, such as air. Lightray 106 can experience subsequent reflections via TIR and thus staywithin the confines of light guide film 104. On the other hand, somelight rays, such as light ray 108, can enter an optical coating 114,strike blazed grating 102, and consequently be directed outside lightguide film 104 and into surrounding medium 112. Such light rays can exitthe light guide film at angles that are relatively small, even afterrefraction at an exit point 116. Exit angles 118 can be measuredrelative to a normal axis 120 perpendicular to the exit surface (e.g.,the surface of light guide film 104). Light rays exiting light guidefilm 104 at angles substantially close to the normal axis can be adesirable feature of light guide 100 for illumination applicationsinvolving LCD displays. However, light guide 100 can have an undesirablefeature: In order to operate properly, material 122 of light guide 100must be air or other gas having a refraction index near 1.0.

In some implementations, structures (e.g., films, layers, coatings) oflight guide film 100 can include any of a number of types of transparentmaterials, such as polymethyl methacrylate (PMMA), polycarbonate (PC),polyethylene, polyethylene terephthalate, polyvinyl butyral, transparentceramics, various glasses, and so on. For example, blazed grating 102can include a micro structure fabricated by any of a number oftechniques, such as hot embossing, injection molding, or with a lacquerlayer on foil, just to name a few examples.

FIG. 2 is a close-up view of blazed grating 102 of light guide 100. Afirst side of optical coating 114 includes grating 102 and an oppositeside 202 includes an interface between the optical coating and lightguide film 104. Grating 102, as shown, has a line spacing 204 and atriangular, sawtooth-shaped cross section, forming a step structure.Blaze angles 206 and 208 can be adjusted to maximize diffractionefficiency for a particular wavelength of light. For a particularnumerical example, angle 206 can be about 88.0 degrees and angle 208 canbe about 43.5 degrees.

A properly operating light guide 100 provides light rays exiting withina few degrees of normal to the light guide. Such exiting light rays canbe used for illumination applications involving LCD displays. Asmentioned above, however, for proper operation, blazed grating 102 oflight guide 100 cannot be optically coupled to any materials other thanair or other low-index materials (e.g., indices of refractionsubstantially near 1.0). For example, if surrounding medium 122 includesan optical coating having an index of refraction of about 1.3 thenblazed grating 102 will not properly diffract light. Blazed grating 102operates by bending light rays using more than one grating element. Forexample, a single grating (one triangular pattern) will produce weaklycollimated light. On the other hand, multiple grating elements close toone another work together to change the direction of propagating light.However, the angle of light can to a point where the light no longertravels through additional grating elements but is reflected at anglesclose to surface normal by TIR. However, light bending (by TIR) thatyields reflected light close to surface normal cannot occur in a mediumhaving a certain range of refractive indices, such as 1.3 or above.

FIG. 3 is a cross-section of a light guide 300, according to someembodiments. Two example light rays 302 and 304 are shown. Light cantravel within light guide film 306 via TIR. For example, light ray 304internally reflects at a point 308 of an interface between light guidefilm 306 and a surrounding medium 310, which can include air. Light ray304 can experience subsequent reflections via TIR and can thus staywithin the confines of light guide film 306. On the other hand, somelight rays, such as light ray 302, exit light guide film 306 bypropagating through a first optical layer 312 and into a second opticallayer 324. The first optical layer 312, the second optical layer 324,and a grating pattern 314 comprise a composite optical coating thatcovers at least a portion of light guide film 306. Grating pattern 314is configured to out-couple light rays travelling in the light guidefilm. For example, the grating pattern is configured so that light raysthat exit light guide film 306 transmit through grating pattern 314twice before being total internally reflected by the grating pattern atan angle that out-couples the exiting light rays. As indicated by 344,light ray 302 then reflects, via TIR, off an interface between secondoptical layer 324 and a non-gas low-refractive index (LRI) boundarylayer 328. The reflected light ray strikes a first portion 346 ofgrating pattern 314 that, via refraction, redirects the light ray towarda second portion 348 of grating pattern 314. Based, at least in part, onthe difference of refractive indices of first and second optical layers312 and 314 and an angle at which the light ray is refracted from firstportion 346, grating pattern 314 reflects, via TIR, the light ray intolight guide film 306. The light ray crosses the light guide film 306 ina final pass at a sufficiently small angle (relative to a normal axis318) that allows the light ray to exit light guide film 306 and entersurrounding medium 310. Though grating pattern 314 can direct suchexiting light rays at angles 316 that are sufficiently small to allowthe light rays to exit light guide film 306, these angles are relativelylarge (e.g., greater than about 10.0 degrees) compared to angles ofexiting light rays produced by a blazed grating, such as that shown inthe example embodiment of FIG. 1. Refraction at exit point 320 canfurther increase the exiting angle. Light ray 322 exiting light guidefilm 306 at such relatively large angles can be undesirable for someillumination applications involving LCD displays. Accordingly, asexplained below, a beam steering structure placed on light guide film306 can steer exiting beams toward the normal axis.

Second optical layer 324, at least partially covering first opticallayer 312, can have an index of refraction substantially less than anindex of refraction of layer 312. As used herein, an index of refractionof one material is “substantially different” than that of anothermaterial if the refractive indices differ by about 5% or more; forexample, the refractive indices may differ by 5.1%, 5.5%, 6.5%. Thus, anindex of refraction of a first material is “substantially less” thanthat of a second material if the refractive index of the first materialis about 5%, or more, lower than the refractive index of the secondmaterial. For example, an index of refraction of layer 324 can be about1.49, and an index of refraction of layer 312 can be about 1.59. In someimplementations non-gas LRI boundary layer 328 can at least partiallycover the second optical layer 324.

In various implementations, a density of grating pattern 314 can bedetermined by an inter-pattern spacing 326. A distribution or uniformityof light exiting light guide 300 can be based, at least in part, on sucha grating pattern density. Though example light ray 302 is shown in FIG.3 to cross the first-second optical layer interface in an inter-patternspacing 326, a light ray crossing this interface in the grating pattern314 can still experience a first TIR, refraction, and a second TIR, suchas experienced by light ray 302 at 344, 346, and 348, respectively.

In some implementations, light guide 300 can include one or more passiveoptical layers between, among, above or below light guide film 306,surrounding medium 310, first optical layer 312, second optical layer324 and LRI boundary layer 328. An optical layer is considered passiveif the optical layer does not affect the angle of travel of a light ray.For example, any homogeneous layer of material having a constantthickness can behave as a passive layer (e.g., a layer of glass orplastic). This is because light that bends (refracts) by a particularangle upon entering the passive layer will un-bend by the same angleupon exiting the passive layer, resulting in a net direction change ofzero. More particularly, light refraction angles are not substantiallyaffected (e.g., refractive angle changes of less than 2.0 degrees) bythe presence of a passive optical layer, except within the optical layeritself. For example, if light exits at a particular exit angle from astack of optical layers, adding a passive layer anywhere into the stackwill not change the exit angle. As another example, one or more passiveoptical layers (not shown) between or among light guide film 306,surrounding medium 310, first optical layer 312, second optical layer324 and/or LRI boundary layer 328 would not affect trajectory angles oflight ray 302 at 344, 346, 348 or 320. There are a number of reasons whyan optical stack may include a passive layer. For example, a passivelayer can add physical strength to an optical stack. In another example,a passive layer can be a by-product (e.g., relic) of a process thatfabricates an optical stack. In yet another example, a passive layer canbe used as a physical spacer to acquire a particular thickness of aportion of an optical stack.

In some embodiments, the refractive index of light guide film 306 may besubstantially the same (e.g., within 2%) as that of first optical layer312. Accordingly, the optical interface between light guide film 306 andfirst optical layer 312 is optically passive. In such a case, trajectoryangles of light ray 302 at 344, 346, 348 or 320 would be the samewhether grating pattern 314 is at the interface between first opticallayer 312 and second optical layer 324 (e.g., as shown in FIG. filmlayer 3), or is at the interface between light guide film 306 and secondoptical layer 324—without including the first optical layer 312 betweenoptical layers 306 and 324.

FIG. 4 is a close-up view of grating pattern 314 of light guide 300,according to some embodiments. A side of second optical layer 312includes grating pattern 314 and an opposite side 402 includes aninterface between the second optical layer and light guide film 306.First optical layer 324 at least partially covers the grating pattern.Grating pattern 314, as shown, has a line spacing 404 and a triangular,sawtooth-shaped cross section, forming a step structure. Pattern angles406 and 408 can be adjusted to maximize refraction efficiency for aparticular wavelength of light.

For a particular numerical example, angle 406 can be about 72.69 degreesand angle 408 can be about 31.69 degrees. Though such example angles areprovided with a particular accuracy (e.g., to the nearest hundredth of adegree), angles need not be so precise. Moreover, pattern angles 406and/or 408 can be changed to compensate for different refractiveindices. In various implementations, some parameters of grating pattern314, such as line spacing 404 and pattern angles 406 and 408, can beselected based, at least in part, on display size, light source (e.g.,LEDs) type, light source positions, and so on.

Grating pattern 314 can include a micro structure fabricated by any of anumber of techniques, such as hot embossing, injection molding, or witha lacquer layer on foil, just to name a few examples. Examples of suchoptical lacquer can include, for example, an optical lacquer such asNalax3®, manufactured by Nanocomp Oy Ltd. of Lehmo, Finland, opticallacquers manufactured by SKC of Seoul, Korea, or other optical lacquers.

FIG. 5 is a cross-section of a laminated collimator 500 including a beamsteering structure 502 and a light guide 504. As mentioned above, lightrays exiting a light guide at relatively large angles can be undesirablefor any of a number of applications, such as illumination applicationsinvolving LCD displays. Accordingly, beam steering structure 502 can beplaced on light guide 504 to steer exiting beams toward the normal axisof the light guide.

As described above, light can travel within a light guide film 506 viaTIR. A portion of light rays, such as 508, can transmit through a firstoptical layer 510 and into a second optical layer 538. Grating pattern512 in the first optical layer can be configured to out-couple lightrays travelling in the light guide film. The first optical layer 510,the second optical layer 538, and grating pattern 512 comprise acomposite optical coating that covers at least a portion of light guidefilm 506. Grating pattern 512 is configured to out-couple light raystravelling in the light guide film. For example, the grating pattern isconfigured so that light rays that exit light guide film 506 transmitthrough grating pattern 512 twice before being total internallyreflected by the grating pattern at an angle that out-couples theexiting light rays.

As indicated by 544, light ray 508 reflects, via TIR, off an interfacebetween second optical layer 538 and a non-gas low-refractive index(LRI) boundary layer 540. The reflected light ray strikes a firstportion 546 of grating pattern 512 that, via refraction, redirects thelight ray toward a second portion 548 of grating pattern 512. Based, atleast in part, on the difference of refractive indices of first andsecond optical layers 510 and 538 and an angle at which the light ray isrefracted from first portion 546, grating pattern 512 reflects, via TIR,the light ray into light guide film 506. The light ray crosses the lightguide in a final pass at a sufficiently small angle (relative to an axisnormal to surface of 506) that allows the light ray to exit light guidefilm 506 and enter a beam steering structure 502.

Though grating pattern 512 can direct light rays at angles that aresufficiently small to allow the light rays to exit light guide 504,these angles are undesirably large (e.g., greater than about 10.0degrees) for a number of applications involving LCD displays. Refractionat exit point 532 can further increase the exiting angle. Beam steeringstructure 502 placed on light guide 504, however, can steer exitingbeams toward the normal axis. For example, beam steering structure 502can bend light ray 508 exiting light guide 504 so that the light ray (aslight ray 514) exits laminated collimator 500 at an angle 516 that isrelatively small (e.g., less than about 5 degrees), measured relative tonormal axis 518 perpendicular to the exit surface (e.g., the surface ofbeam steering structure 502). Such light rays exiting a collimator atangles substantially close to the normal axis 518 can be a desirablefeature for a number of applications, including illuminationapplications involving LCD displays.

In detail, beam steering structure 502 includes transmissive elements,including a number of patterned layers. For example, a first patternedlayer 520 includes a first pattern 522 and a second patterned layer 524includes a second pattern 526. First and second patterns can becontinuous, or, like grating pattern 512 one or both can include aninter-pattern spacing similar to 528. First and second patterns need notaffect distribution of light exiting laminated collimator 500. Beamsteering structure 502 can also include a surface film 530 at leastpartially covering first patterned layer 520.

Light ray 508 refracts as it exits light guide film 506 and enters beamsteering structure 502 at point 532. The refracted light ray strikes afirst portion 550 of grating pattern 526 that, via refraction, redirectsthe light ray toward a second portion 552 of grating pattern 526. Based,at least in part, on the difference of refractive indices of secondpatterned layers 524 and an LRI interface layer 536 and an angle atwhich the light ray is refracted from first portion 550, grating pattern526 reflects, via TIR, the light ray toward first pattern 522.

By refraction, the first pattern 522 bends the light ray as the lightray transits first pattern 522 at point 534. The interface between firstpatterned layer 520 and surface film 530 and the exit surface of surfacefilm 530 further bend the light ray toward axis 518 via refraction.

In some embodiments, beam steering structure 502 can be opticallycoupled to light guide 506 via LRI interface layer 536. Light guide 504can further include second optical layer 538 and an LRI boundary layer540. Optical coupling can be performed by laminating beam steeringstructure 502 to light guide 504 using LRI interface layer 536 as anadhesive. In an implementation, LRI interface layer 536 and LRI boundarylayer 540 can include the same material. In one example, such a materialcan include an optically clear adhesive (OCA) silicone.

In some implementations, structures (e.g., films, layers, coatings) oflaminated collimator 500 can include any of a number of types oftransparent materials, such as polymethyl methacrylate (PMMA),polycarbonate (PC), polyethylene, polyethylene terephthalate, polyvinylbutyral, transparent ceramics, various glasses, and so on. Fabricationprocesses include thin film vapor deposition, printing, etching, and soon.

Herein, “optically coupled” can be used to refer to two or more portionscomprising layers or an assembly of layers that are mutually arranged sothat light in one portion can travel into another portion. For example,an optical layer can be optically coupled to a light guide film when theoptical layer and the light guide film physically contact one another.In another related example, an optical layer can be optically coupled toa light guide film when the optical layer and the light guide film arephysically separated from each other by a relatively small gap. Eventhough, in this case, transfer of light from the optical layer to thelight guide film can be less efficient compared to the case where theoptical layer and the light guide film are in contact with each other,the optical layer and the light guide film are nevertheless opticallycoupled to one another.

In some embodiments, a light guide film, first and second patternedlayers (e.g., of a beam steering structure), first and second opticallayers (e.g., of a laminated collimator), and LRI layers include any ofa number of transparent glass or plastic materials, such as siliconeOCA, lacquer, PET, PMMA, or PC, just to name a few examples. Whileselecting particular materials for the light guide and the variousoptical or patterned layers, indices of refraction of the materials canbe considered. For example, a light guide film can include polycarbonateor other plastic. First and second optical layers and first and secondpatterned layers can include optical lacquers. For example, in someimplementations, first patterned layer 520 can include a same materialas that of first optical layer 510. Also, second patterned layer 524 caninclude a same material as that of second optical layer 538.

Such materials can satisfy criteria for desirable operation of alaminated collimator. For example, an index of refraction of secondoptical layer 538 can be substantially less than an index of refractionof the light guide film. Also, an index of refraction of first opticallayer 510 can be substantially the same as the refractive index of thelight guide film and substantially greater than the second optical layer538. Also, an index of refraction of the LRI boundary layer can besubstantially less than refractive indices of the light guide film, thefirst optical layer, and the second optical layer.

As mentioned above, a laminated collimator need not be surrounded byair, for example, for proper operation. Instead, a laminated collimatorcan operate in any medium 542, which can provide an advantage in that anindex of refraction of 542 need not be considered for proper operationof laminated collimator 500.

In some implementations, laminated collimator 500 can include one ormore passive optical layers between, among, above or below light guidefilm 506, first optical layer 510, second optical layer 538, LRIboundary layer 540, second patterned layer 524, surface film 530, firstpatterned layer 520 and LRI interface layer 536. For example, one ormore passive optical layers (not shown) between or among these layers orfilms would not affect trajectory angles of light ray 508 at 544, 546,548, 532, 550, 552 or 534.

In some embodiments, the refractive index of light guide film 506 may besubstantially the same (e.g., within 2%) as that of first optical layer510. Accordingly, the optical interface between light guide film 506 andfirst optical layer 510 is optically passive. In such a case, trajectoryangles of light ray 508 at 544, 546, 548, 532, 550, 552 or 534 would bethe same whether grating pattern 512 is at the interface between firstoptical layer 510 and second optical layer 538 (e.g., as shown in FIG.5), or is at the interface between light guide film 506 and secondoptical layer 538—without including the first optical layer 510 betweenoptical layers 506 and 538.

FIG. 6 is a close-up view of grating patterns of beam steering structure502, according to some embodiments. First patterned layer 520 caninclude a first pattern 522 and second patterned layer 524 can include asecond pattern 526. First pattern 522, as shown, has a line spacing 602,a triangular, sawtooth-shaped cross section, and pattern angles 604 and606. For a particular numerical example, angle 604 can be about 53.43degrees and angle 606 can be about 84.77 degrees. Second pattern 526, asshown, has a line spacing 608, a triangular, sawtooth-shaped crosssection, and pattern angles 610 and 612. For a particular numericalexample, angle 610 can be about 88.84 degrees and angle 612 can be about58.25 degrees.

Line spacing and pattern angles of the first and second patterns can beadjusted or selected based, at least in part, on display size, lightsource (e.g., LEDs) type, light source positions, and so on. Positionsor phases of first pattern 522 and second pattern 526 need not besynchronously positioned with one another. Accordingly, fabrication ofbeam steering structure 502 can thus be relatively simple. In someimplementations, second pattern 526 can be at least partially covered byLRI interface layer 536.

First and second patterns can include a micro structure fabricated byany of a number of techniques, such as hot embossing, injection molding,or with a lacquer layer on foil, just to name a few examples.

FIGS. 7A-7E show a process of fabricating a laminated collimator byforming a light guide and a beam steering structure. Such a process canbegin by at least partially covering a light guide film 702 with a firstoptical layer 704, as shown in FIG. 7A. For example, optical layer 704can be a lacquer including a grating pattern 706. In some embodiments, agrating can be manufactured by a roll-to-roll (R2R) method, involvingapplying liquid lacquer on plastic foil to produce a form, and thentransferring the form via drum tool to a lacquer film. Lacquer cansimultaneously harden, for example, by exposure to UV light. The drumtool or a belt can have a negative pattern that has been manufacturedfrom a master by electroforming. For example, a master can be fabricatedusing e-beam, laser lithography, or mechanical grinding processes.

In FIG. 7B, a second optical layer 708 is applied to first optical layer704 so as to cover grating pattern 706. With an addition of an optionalLRI boundary layer 710 covering second optical layer 708, a resultingstructure can include a light guide 724 as shown in FIG. 7E.

In FIG. 7C, fabricating a beam steering structure can begin by applyinga first patterned layer 712 to a surface layer 714. First patternedlayer 712 includes a first pattern 716. In FIG. 7D, a second patternedlayer 718 can be applied to first patterned layer 712. Second patternedlayer 718 includes a second pattern 720. A resulting structure includesa beam steering structure 726 as shown in FIG. 7E.

Arrows 722 in FIG. 7E indicate that light guide 724 and beam steeringstructure 726 can be brought together so as to be optically coupled toone another. An interstitial space between the laminated collimator andthe beam steering structure can be filled with LRI material 728 to forman LRI interface layer. In some implementations, LRI material 728 can bean optical adhesive, which can bond light guide 724 and beam steeringstructure 726 together to form a laminated collimator, such as laminatedcollimator 500 shown in the example embodiment of FIG. 5.

FIG. 8A is a plot 800 for describing a distribution of light exiting alaminated collimator, according to various embodiments. In particular,line 802 can include a plot of relative intensity of light exiting anoptical surface as a function of exit angle. As described above, an exitangle can include an angle of exiting light measured from an axis normalto the exit surface. For example, returning to FIG. 5, angle 516 oflight exiting beam steering structure 502 can include an exit angleplotted along the horizontal axis of plot 800.

In this particular example embodiment, line 802 includes a primary peak804 at an exit angle α and a secondary peak 806 at an exit angle β.Primary peak 804 corresponds to a distribution of relatively small exitangles for light exiting a beam steering structure of a laminatedcollimator. As mentioned above, such small angles can be desirable for anumber of applications. For example, angle α can be about 5 to 10degrees.

Secondary peak 806 corresponds to a distribution of relatively largeexit angles for light exiting the beam steering structure of thelaminated collimator. Exit angle β can be about 50 to 60 degrees, thoughclaimed subject matter is not limited to any particular angles. Light insuch a secondary peak corresponds to stray light propagating through alaminated collimator. In some implementations, a second patterned layer(e.g., 524, shown in FIG. 5) of a beam steering structure can, at leastin part, direct stray light to exit angles of a secondary peak.

FIG. 8B is a close-up view of grating patterns of a portion of a beamsteering structure 808, according to various embodiments. Firstpatterned layer 810 can include a first pattern 812 and second patternedlayer 814 can include a second pattern 816. An LRI interface layer 818at least partially covers second patterned layer 814. Two example lightrays 820 and 822 are shown interacting with first and second patternedlayers in FIG. 8. In particular, light ray 820 crosses portion 824 ofsecond pattern 816 and refracts toward portion 826 that in turnreflects, via TIR, light ray 820 toward a portion 828 of first pattern812. Portion 828 of first pattern 812 subsequently refracts light ray820 toward an exit angle that falls in an angular range of primary peak804, shown in FIG. 8A. In contrast, light ray 822 follows a path towardan exit angle that falls in an angular range of secondary peak 806. Inparticular, light ray 822 crosses portion 830 of second pattern 816 andrefracts toward an upper portion 832 of second pattern 816. However,light ray 822 is refracted in such a direction so as to miss strikingupper portion 832. Instead, light ray 822 proceeds, without reflectingfrom any portion of second pattern 816, toward a portion 834 of firstpattern 812. The lack of reflection from second pattern 816 leads tofirst pattern 812 subsequently refracting light ray 822 toward an exitangle that falls in an angular range of secondary peak 806, shown inFIG. 8A.

As described below, an amount of light exiting at a secondarydistribution of peak angles can be reduced by incorporating more thanone beam steering structure (e.g., a beam steering stack) on a laminatedcollimator.

FIG. 9 is a laminated collimator 900 including a beam steering stack 902and a light guide 904, according to some embodiments. As mentionedabove, a beam steering structure can be combined with a light guide tosteer exiting beams toward a normal axis of the light guide. An exampleembodiment of such a case is shown in FIG. 5. In the embodiment of FIG.9, beam steering stack 902 comprising multiple beam steering structures906, 908, 910, and so on, can be placed on light guide 904 to furthersteer exiting beams toward the normal axis of the light guide. In otherwords, light-bending features of beam steering structures can becumulative. For example, if one beam steering structure bends a lightray by 2 degrees, then two such beam steering structures can bend thesame light ray by 4 degrees. Patterned layers of such beam steeringstructures, however, can be used to steer light by other angles, and anamount of light bending may be different for different beam steeringstructures.

A principle of operation of a beam steering structure is based, at leastin part, on the fact that a light ray refracts (e.g., is bent) in aboundary between two materials having different refractive indices,except when the light ray perpendicularly hits the boundary. In thisspecial case, the light ray preserves its angle while passing throughthe boundary. From a collimation point of view that desires an exitangle close to the normal of an exit surface, a flat boundary without apattern can improve the ray angle when the light ray passes from lowrefractive index material to high refractive index material, regardlessof the incident angle. On the other hand, when light is passing aboundary from high refractive index material to low refractive indexmaterial the gained benefit in ray angle is lost.

First patterned layer 926, first pattern 928, second patterned layer930, and second pattern 932 can be designed so that a light ray isrefracted (e.g., bent) at portions of a boundary that is flat, without apattern, while passing from low refractive index material to highrefractive index material. Once the light ray passes from highrefractive index material to low refractive index material it sees apatterned portion of a boundary where pattern orientation is such thatthe light ray hits a face of the patterned portion perpendicularly. Inthis way, the gained light ray bending by the flat portion of thepattern can be preserved while the light ray passes through highrefractive index material to low refractive index material.

As described above, light can travel within a light guide film 912 viaTIR. A portion of light rays, such as 934, can strike a grating pattern928 and consequently be directed outside light guide film 912 and intofirst beam steering structure 906, which can bend the light ray by aparticular angle. The light ray subsequently travels into second beamsteering structure 908, which can additionally bend the light ray by aparticular angle. The light ray again travels into another beam steeringstructure 910, which can additionally bend the light ray, and so on.Accordingly, a resulting light ray 918 can exit the laminated collimatorat angles that are relatively small, measured relative to a normal axis920 perpendicular to the exit surface (e.g., the surface of beamsteering stack 902). On the other hand, a beam steering stack can bendlight in any direction, including directions having angles that arelarge (e.g., within a few degrees of parallel to the exit surface).Small exit angles or large exit angles, for example, can be desirablefor different applications. In some implementations, direction of beamsteering and/or number of beam steering structures in a beam steeringstack can be based, at least in part, on differences between refractionindices of patterned layers 914 and 908 of individual beam steeringstructures.

As described above, beam steering stack 902 can include individual beamsteering structures (e.g., 906, 908, and so on) including a number ofpatterned layers and a surface film 922. For example, individual beamsteering structure 924 can include first patterned layer 926 having afirst pattern 928 and second patterned layer 930 having a second pattern932. First patterned layer 926 and second patterned layer 930 can havean index of refraction different from one another. For example, firstpatterned layer 926 can have an index of refraction of about 1.59 whilesecond patterned layer 930 can have an index of refraction of about1.49, though indices of refraction of patterned layers can be any value,and claimed subject matter is not limited in this respect. Accordingly,beam steering of light (e.g., ray 934) can occur via refraction based ona difference of refraction indices of first and second patterned layers926 and 930. Patterns 928 and 932 can further contribute to beamsteering by preserving such refraction.

FIG. 10 illustrates an example electronic device 1000 that may includethe example display assemblies discussed above. The device 1000 maycomprise any type of electronic device having a display. For instance,the device 1000 may be a mobile electronic device (e.g., an electronicbook reader, a tablet computing device, a laptop computer, a smart phoneor other multifunction communication device, a portable digitalassistant, a wearable computing device, an automotive display, etc.).Alternatively, the device 1000 may be a non-mobile electronic device(e.g., a computer display, a television, etc.). In addition, while FIG.10 illustrates several example components of the electronic device 1000,it is to be appreciated that the device 1000 may also include otherconventional components, such as an operating system, system busses,input/output components, and the like. Further, in other examples, suchas in the case of a television or computer monitor, the electronicdevice 100 may only include a subset of the components shown.

Regardless of the specific implementation of the electronic device 1000,the device 1000 includes a display 1002 and a corresponding displaycontroller 1004. The display 1002 may represent a reflective display insome instances, such as an electronic paper display, a reflective LCDdisplay, or the like. Electronic paper displays represent an array ofdisplay technologies that largely mimic the look of ordinary ink onpaper. In contrast to conventional backlit displays, electronic paperdisplays typically reflect light, much as ordinary paper does. Inaddition, electronic paper displays are often bi-stable, meaning thatthese displays are capable of holding text or other rendered images evenwhen very little or no power is supplied to the display. Some examplesof the display 1002 that may be used with the implementations describedherein include bi-stable LCD displays, micro electromechanical system(MEMS) displays, such as interferometric modulator displays, cholestericdisplays, electrophoretic displays, electrofluidic pixel displays,electrowetting displays, photonic ink displays, gyricon displays, andthe like. In other implementations, or for other types of devices 1000,the display 1002 may be an active display such as a liquid crystaldisplay, a plasma display, a light emitting diode display, an organiclight emitting diode display, and so forth. Accordingly, implementationsherein are not limited to any particular display technology.

In one implementation, the display 1002 comprises an electrophoreticdisplay that moves particles between different positions to achievedifferent color shades. For instance, in a pixel that is free from acolor filter, the pixel may be configured to produce white when theparticles within this pixel are located at the front (i.e., viewing)side of the display. When situated in this manner, the particles reflectincident light, thus giving the appearance of a white pixel. Conversely,when the particles are pushed near the rear of the display, the displayabsorbs the incident light and, hence, causes the pixel to appear blackto a viewing user. In addition, the particles may situate at varyinglocations between the front and rear sides of the display to producevarying shades of gray. Furthermore, as used herein, a “white” pixel maycomprise any shade of white or off white, while a “black” pixel maysimilarly comprise any shade of black.

In another implementation, the display 1002 comprises an electrophoreticdisplay that includes oppositely charged light and dark particles. Inorder to create white, the display controller moves the light particlesto the front side of the display by creating a corresponding charge atan electrode near the front and moves the dark particles to the back ofthe display by creating a corresponding charge at an electrode near theback. In order to create black, meanwhile, the controller changes thepolarities and moves the dark particles to the front and the lightparticles to the back. Furthermore, to create varying shades of gray,the controller 1004 may utilize different arrays of both light and darkparticles. In some cases, the particles may be contained in tinyindividual transparent capsules, such as approximately 40 micrometers indiameter. The capsules are suspended in a fluid, such as a liquidpolymer, between a transparent upper electrode grid layer and a lowerelectrode grid layer separated by a gap, such as approximately 50-200micrometers.

In still another implementation, the display comprises an electrowettingdisplay that employs an applied voltage to change the surface tension ofa liquid in relation to a surface. For instance, by applying a voltageto a hydrophobic surface, the wetting properties of the surface can bemodified so that the surface becomes increasingly hydrophilic. As oneexample of an electrowetting display, the modification of the surfacetension acts as an optical switch by contracting a colored oil film whena voltage is applied to individual pixels of the display. When thevoltage is absent, the colored oil forms a continuous film within apixel, and the color may thus be visible to a user of the display. Onthe other hand, when the voltage is applied to the pixel, the coloredoil is displaced and the pixel becomes transparent. When multiple pixelsof the display are independently activated, the display can present acolor or grayscale image. The pixels may form the basis for atransmissive, reflective, or transmissive/reflective (transreflective)display. Further, the pixels may be responsive to high switching speeds(e.g., on the order of several milliseconds), while employing smallpixel dimensions. Accordingly, the electrowetting displays herein may besuitable for applications such as displaying video content. In addition,the lower power consumption of electrowetting displays in comparison toconventional LCD displays makes the technology suitable for displayingcontent on portable devices that rely on battery power.

Of course, while several different examples have been given, it is to beappreciated that the reflective displays described herein may compriseany other type of electronic-paper technology or reflective-displaytechnology, examples of which are provided above. In addition, whilesome of the examples described above are discussed as rendering black,white, and varying shades of gray, it is to be appreciated that thedescribed techniques apply equally to reflective displays capable ofrendering color pixels. As such, the terms “white,” “gray,” and “black”may refer to varying degrees of color in implementations utilizing colordisplays. For instance, where a pixel includes a red color filter, a“gray” value of the pixel may correspond to a shade of pink while a“black” value of the pixel may correspond to a darkest red of the colorfilter. Furthermore, while some examples herein are described in theenvironment of a reflective display, in other examples, the display 102may represent a backlit display, examples of which are mentioned above.

In addition to including the display 1002, FIG. 10 illustrates that someexamples of the device 1000 may include a touch sensor component 1006and a touch controller 1008. In some instances, at least one touchsensor component 1006 resides with, or is stacked on, the display 1002to form a touch-sensitive display (e.g., an electronic papertouch-sensitive display). Thus, the display 1002 may be capable of bothaccepting user touch input and rendering content in response to orcorresponding to the touch input. As several examples, the touch sensorcomponent 1006 may comprise a capacitive touch sensor, a force sensitiveresistance (FSR), an interpolating force sensitive resistance (IFSR)sensor, or any other type of touch sensor. In some instances, the touchsensor component 1006 is capable of detecting touches as well asdetermining an amount of pressure or force of these touches.

FIG. 10 further illustrates that the electronic device 1000 may includeone or more processors 1010 and one or more computer-readable media1012, as well as a front light component 1014 (which may alternativelybe a backlight component in the case of a backlit display) for lightingthe display 1002, a cover layer component 1016, such as a cover glass orcover sheet, one or more communication interfaces 1018 and one or morepower sources 1020. The communication interfaces 1018 may support bothwired and wireless connection to various networks, such as cellularnetworks, radio, WiFi networks, short range networks (e.g., Bluetooth®),infrared (IR), and so forth.

Depending on the configuration of the electronic device 1000, thecomputer-readable media 1012 (and other computer-readable mediadescribed throughout) is an example of computer storage media and mayinclude volatile and nonvolatile memory. Thus, the computer-readablemedia 1012 may include, but is not limited to, RAM, ROM, EEPROM, flashmemory, or other memory technology, or any other medium that can be usedto store computer-readable instructions, programs, applications, mediaitems, and/or data which can be accessed by the electronic device 1000.

The computer-readable media 1012 may be used to store any number offunctional components that are executable on the processor 1010, as wellcontent items 1022 and applications 1024. Thus, the computer-readablemedia 1012 may include an operating system and a storage database tostore one or more content items 1022, such as eBooks, audio books,songs, videos, still images, and the like. The computer-readable media1012 of the electronic device 1000 may also store one or more contentpresentation applications to render content items on the device 1000.These content presentation applications may be implemented as variousapplications 1024 depending upon the content items 1022. For instance,the content presentation application may be an electronic book readerapplication for rending textual electronic books, an audio player forplaying audio books or songs, a video player for playing video, and soforth.

In some instances, the electronic device 1000 may couple to a cover (notshown in FIG. 10) to protect the display (and other components in thedisplay stack or display assembly) of the device 1000. In one example,the cover may include a back flap that covers a back portion of thedevice 1000 and a front flap that covers the display 1002 and the othercomponents in the stack. The device 1000 and/or the cover may include asensor (e.g., a hall effect sensor) to detect when the cover is open(i.e., when the front flap is not atop the display and othercomponents). The sensor may send a signal to the front light component1014 when the cover is open and, in response, the front light component1014 may illuminate the display 1002. When the cover is closed,meanwhile, the front light component 1014 may receive a signalindicating that the cover has closed and, in response, the front lightcomponent 1014 may turn off.

Furthermore, the amount of light emitted by the front light component1014 may vary. For instance, upon a user opening the cover, the lightfrom the front light may gradually increase to its full illumination. Insome instances, the device 1000 includes an ambient light sensor (notshown in FIG. 1) and the amount of illumination of the front lightcomponent 1014 may be based at least in part on the amount of ambientlight detected by the ambient light sensor. For example, the front lightcomponent 1014 may be dimmer if the ambient light sensor detectsrelatively little ambient light, such as in a dark room; may be brighterif the ambient light sensor detects ambient light within a particularrange; and may be dimmer or turned off if the ambient light sensordetects a relatively large amount of ambient light, such as directsunlight.

In addition, the settings of the display 1002 may vary depending onwhether the front light component 1014 is on or off, or based on theamount of light provided by the front light component 1014. Forinstance, the electronic device 1000 may implement a larger default fontor a greater contrast when the light is off compared to when the lightis on. In some instances, the electronic device 1000 maintains, when thelight is on, a contrast ratio for the display that is within a certaindefined percentage of the contrast ratio when the light is off.

As described above, the touch sensor component 1006 may comprise acapacitive touch sensor that resides atop the display 1002. In someexamples, the touch sensor component 1006 may be formed on or integratedwith the cover layer component 1016. In other examples, the touch sensorcomponent 1006 may be a separate component in the stack of the displayassembly. The front light component 1014 may reside atop or below thetouch sensor component 1006. In some instances, either the touch sensorcomponent 1006 or the front light component 1014 is coupled to a topsurface of a protective sheet 1026 of the display 1002. As one example,the front light component 1014 may include a lightguide sheet and alight source (not shown in FIG. 10). The lightguide sheet may comprise asubstrate (e.g., a transparent thermoplastic such as PMMA or otheracrylic), a layer of lacquer and multiple grating elements formed in thelayer of lacquer that function to propagate light from the light sourcetowards the display 1002, thus illuminating the display 1002.

The cover layer component 1016 may include a transparent substrate orsheet having an outer layer that functions to reduce at least one ofglare or reflection of ambient light incident on the electronic device1000. In some instances, the cover layer component 1016 may comprise ahard-coated polyester and/or polycarbonate film, including a basepolyester or a polycarbonate, that results in a chemically bondedUV-cured hard surface coating that is scratch resistant. In someinstances, the film may be manufactured with additives such that theresulting film includes a hardness rating that is greater than apredefined threshold (e.g., at least a hardness rating that is resistantto a 3 h pencil). Without such scratch resistance, a device may be moreeasily scratched and a user may perceive the scratches from the lightthat is dispersed over the top of the reflective display. In someexamples, the protective sheet 1026 may include a similar UV-cured hardcoating on the outer surface. The cover layer component 1016 may coupleto another component or to the protective sheet 1026 of the display1002. The cover layer component 1016 may, in some instances, alsoinclude a UV filter, a UV-absorbing dye, or the like, for protectingcomponents lower in the stack from UV light incident on the electronicdevice 1000. In still other examples, the cover layer component 1016 mayinclude a sheet of high-strength glass having an antiglare and/orantireflective coating.

The display 1002 includes the protective sheet 1026 overlying animage-displaying component 1028. For example, the display 1002 may bepreassembled to have the protective sheet 1026 as an outer surface onthe upper or image-viewing side of the display 1002. Accordingly, theprotective sheet 1026 may be integral with and may overlie theimage-displaying component 1028. The protective sheet 1026 may beoptically transparent to enable a user to view, through the protectivesheet 1026, an image presented on the image-displaying component 1028 ofthe display 1002.

In some examples, the protective sheet 1026 may be a transparent polymerfilm in the range of 25 to 200 micrometers in thickness. As severalexamples, the protective sheet may be a transparent polyester, such aspolyethylene terephthalate (PET) or polyethylene naphthalate (PEN), orother suitable transparent polymer film or sheet, such as apolycarbonate or an acrylic. In some examples, the outer surface of theprotective sheet 126 may include a coating, such as the hard coatingdescribed above. For instance, the hard coating may be applied to theouter surface of the protective sheet 1026 before or after assembly ofthe protective sheet 1026 with the image-displaying component 1028 ofthe display 1002. In some examples, the hard coating may include aphotoinitiator or other reactive species in its composition, such as forcuring the hard coating on the protective sheet 1026. Furthermore, insome examples, the protective sheet 1026 may be dyed with aUV-light-absorbing dye, or may be treated with other UV-absorbingtreatment. For example, the protective sheet may be treated to have aspecified UV cutoff such that UV light below a cutoff or thresholdwavelength is at least partially absorbed by the protective sheet 1026,thereby protecting the image-displaying component 1028 from UV light.

According to some implementations herein, one or more of the componentsdiscussed above may be coupled to the display 1002 using a liquidoptically clear adhesive (LOCA). For example, suppose that the lightguide portion of the front light component 1014 is to be coupled to thedisplay 1002. The light guide may be coupled to the display 1002 byplacing the LOCA on the outer or upper surface of the protective sheet1026. When the LOCA reaches the corner(s) and/or at least a portion ofthe perimeter of protective sheet, UV-curing may be performed on theLOCA at the corners and/or the portion of the perimeter. Thereafter, theremaining LOCA may be UV-cured and the front light component 1014 may becoupled to the LOCA. By first curing the corner(s) and/or perimeter, thetechniques effectively create a barrier for the remaining LOCA and alsoprevent the formation of air gaps in the LOCA layer, thereby increasingthe efficacy of the front light component 1014. In otherimplementations, the LOCA may be placed near a center of the protectivesheet 1026, and pressed outwards towards a perimeter of the top surfaceof the protective sheet 126 by placing the front light component 1014 ontop of the LOCA. The LOCA may then be cured by directing UV lightthrough the front light component 1014. As discussed above, and asdiscussed additionally below, various techniques, such as surfacetreatment of the protective sheet, may be used to prevent discolorationof the LOCA and/or the protective sheet 1026.

While FIG. 10 illustrates a few example components, the electronicdevice 1000 may have additional features or functionality. For example,the device 1000 may also include additional data storage devices(removable and/or non-removable) such as, for example, magnetic disks,optical disks, or tape. The additional data storage media may includevolatile and nonvolatile, removable and non-removable media implementedin any method or technology for storage of information, such as computerreadable instructions, data structures, program modules, or other data.In addition, some or all of the functionality described as residingwithin the device 1000 may reside remotely from the device 1000 in someimplementations. In these implementations, the device 1000 may utilizethe communication interfaces 1018 to communicate with and utilize thisfunctionality.

One skilled in the art will realize that a virtually unlimited number ofvariations to the above descriptions is possible, and that the examplesand the accompanying figures are merely to illustrate one or moreparticular implementations.

Conclusion

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described. Rather,the specific features and acts are disclosed as illustrative forms ofimplementing the claims.

One skilled in the art will realize that a virtually unlimited number ofvariations to the above descriptions are possible, and that the examplesand the accompanying figures are merely to illustrate one or moreexamples of implementations.

It will be understood by those skilled in the art that various othermodifications can be made, and equivalents can be substituted, withoutdeparting from claimed subject matter. Additionally, many modificationscan be made to adapt a particular situation to the teachings of claimedsubject matter without departing from the central concept describedherein. Therefore, it is intended that claimed subject matter not belimited to the particular embodiments disclosed, but that such claimedsubject matter can also include all embodiments falling within the scopeof the appended claims, and equivalents thereof.

In the detailed description above, numerous specific details are setforth to provide a thorough understanding of claimed subject matter.However, it will be understood by those skilled in the art that claimedsubject matter can be practiced without these specific details. In otherinstances, methods, apparatuses, or systems that would be known by oneof ordinary skill have not been described in detail so as not to obscureclaimed subject matter.

Reference throughout this specification to “one embodiment” or “anembodiment” can mean that a particular feature, structure, orcharacteristic described in connection with a particular embodiment canbe included in at least one embodiment of claimed subject matter. Thus,appearances of the phrase “in one embodiment” or “an embodiment” invarious places throughout this specification are not necessarilyintended to refer to the same embodiment or to any one particularembodiment described. Furthermore, it is to be understood thatparticular features, structures, or characteristics described can becombined in various ways in one or more embodiments. In general, ofcourse, these and other issues can vary with the particular context ofusage. Therefore, the particular context of the description or the usageof these terms can provide helpful guidance regarding inferences to bedrawn for that context.

What is claimed is:
 1. A device comprising: a light guide film totransport light rays via total internal reflection; and a compositeoptical coating to out-couple light rays travelling in the light guidefilm, wherein the composite optical coating covers at least a portion ofa first side of the light guide film, and wherein the composite opticalcoating comprises: a first optical layer adjacent to the light guidefilm to receive an exiting portion of the light rays; a second opticallayer covering at least a portion of the first optical layer; and agrating pattern located at an interface between the first and the secondoptical layers, wherein the grating pattern is configured so that theexiting portion of the light rays transmit through the grating patternat least twice before being total internally reflected by the gratingpattern at an angle that out-couples the exiting portion of the lightrays.
 2. The device of claim 1, wherein the out-coupled exiting portionof the light rays cross the light guide film after being totalinternally reflected by the grating pattern.
 3. The device of claim 1,further comprising a non-gas, low-refractive index (LRI) boundary layerat least partially covering the second optical layer, wherein arefractive index of the LRI boundary layer comprises a value that allowsthe exiting portion of the light rays to total internally reflect froman interface between the second optical layer and the LRI boundarylayer.
 4. The device of claim 3, wherein a refractive index of thesecond optical layer is less than a refractive index of the firstoptical layer, and wherein the refractive index of the LRI boundarylayer is less than refractive indices of the light guide film, the firstoptical layer, and the second optical layer.
 5. The device of claim 2,further comprising: a beam steering structure covering at least aportion of a second side of the light guide film, wherein the secondside is opposite to the first side, and wherein the beam steeringstructure comprises: a first beam-steering grating pattern configured sothat the light rays that cross the light guide film transmit through thefirst beam-steering grating pattern at least once before being totalinternally reflected by the beam-steering grating pattern; and a secondbeam-steering grating pattern configured so that the light raysreflected from the first beam-steering grating pattern transmit throughthe second beam-steering grating pattern exactly once so as to change adirection of travel of the light rays.
 6. A device comprising: a lightguide film to transport light rays via total internal reflection; afirst optical layer covering at least a portion of a first side of thelight guide film, the first optical layer to receive a portion of thelight rays exiting the light guide film as an exiting portion of thelight rays; a second optical layer covering at least a portion of thefirst optical layer; and a grating pattern located at an interfacebetween the first optical layer and the second optical layer toout-couple light rays travelling in the light guide film, wherein thegrating pattern is configured so that the exiting portion of the lightrays transmit through the grating pattern at least twice before beingtotal internally reflected by the grating pattern.
 7. The device ofclaim 6, wherein the total internal reflection by the grating patternout-couples the exiting portion of the light rays from the device. 8.The device of claim 7, wherein the out-coupled exiting portion of thelight rays cross the light guide film exactly once.
 9. The device ofclaim 6, further comprising a non-gas, low-refractive index (LRI)boundary layer at least partially covering the second optical layer,wherein a refractive index of the LRI boundary layer comprises a valuethat allows the exiting portion of the light rays to total internallyreflect from an interface between the second optical layer and the LRIboundary layer.
 10. The device of claim 9, wherein a refractive index ofthe second optical layer is less than a refractive index of the firstoptical layer, and wherein the refractive index of the LRI boundarylayer is less than refractive indices of the light guide film, the firstoptical layer, and the second optical layer.
 11. The device of claim 6,further comprising: a beam steering structure covering at least aportion of a second side of the light guide film, wherein the secondside is opposite to the first side, and wherein the beam steeringstructure comprises: a first beam-steering grating pattern configured sothat the out-coupled exiting portion of the light rays transmit throughthe first beam-steering grating pattern at least once before being totalinternally reflected by the first beam-steering grating pattern; and asecond beam-steering grating pattern configured so that the light raysreflected from the first beam-steering grating pattern transmit throughthe second beam-steering grating pattern exactly once so as to change adirection of travel of the light rays.
 12. The device of claim 11,wherein the first beam-steering grating pattern and the secondbeam-steering grating pattern are configured to steer the out-coupledexiting portion of the light rays toward a direction normal to the beamsteering structure.
 13. The device of claim 11, further comprising oneor more additional beam steering structures covering at least a portionof the beam steering structure.
 14. The device of claim 11, furthercomprising: one or more passive optical layers between any of the firstoptical layer, the second optical layer, the light guide film, or thebeam steering structure.
 15. The device of claim 6 further comprising:one or more processors; one or more computer memories; and a displaymodule stored on the one or more memories and operable on the one ormore processors to modulate the out-coupled exiting portion of the lightrays.
 16. A method comprising: placing a first optical layer on at leasta portion of a first side of a light guide film, wherein a surface ofthe first optical layer includes a grating pattern; and placing a secondoptical layer on at least a portion of the surface that includes thegrating pattern, wherein the grating pattern is configured so that lightrays exiting from the light guide film transmit through the gratingpattern at least twice before being total internally reflected by thegrating pattern.
 17. The method of claim 16, further comprising: placinga non-gas, low-refractive index (LRI) boundary layer on at least aportion of the second optical layer, wherein the refractive index of theLRI boundary layer is less than refractive indices of the light guidefilm, the first optical layer, and the second optical layer.
 18. Themethod of claim 17, wherein a refractive index of the second opticallayer is less than a refractive index of the first optical layer, andwherein a refractive index of the LRI boundary layer is less thanrefractive indices of the light guide film, the first optical layer, andthe second optical layer.
 19. The method of claim 16, wherein thegrating pattern is configured to out-couple light rays travelling in thelight guide film.
 20. The method of claim 19, further comprising:laminating a beam steering structure to at least a portion of a secondside of the light guide film, wherein the second side is opposite to thefirst side, and wherein the beam steering structure comprises: a firstbeam-steering grating pattern configured so that the out-coupled lightrays transmit through the first beam-steering grating pattern oncebefore being total internally reflected by the first beam-steeringgrating pattern; and a second beam-steering grating pattern configuredso that light rays reflected from the first beam-steering gratingpattern transmit through the second beam-steering grating patternexactly once so as to change a direction of travel of the light rays.